1. Field of the Invention
This invention relates to a wide field eyepiece, and more particularly to an eyepiece having an apparent field of view of 40.degree. or greater for use in a telescope, a microscope or the like.
2. Related Background Art
To make the observation of the whole field of view easily in an eyepiece, it is desirable that the on-axis interval between that lens surface of the eyepiece which is most adjacent to an eye and an eye point (hereinafter referred to as the "eye relief") be at least 80% of the focal length of the entire lens system. However, it is generally known that if the apparent field of view is made greater with the various aberrations of rays of light in the margin of field of view of the eyepiece kept constant, the eye relief will become smaller.
It is also known that if the eye relief is made greater, with the apparent field of view kept constant, the lens diameter of the eyepiece will be increased with a result that the various aberrations, particularly coma, astigmatism, chromatic difference of magnification and distortion, of rays of light in the margin of the field of view will be suddenly aggravated.
As described above, in the eyepiece according to the prior art, it has been difficult to correct various aberrations well to the margin of the field of view and yet secure both the field of view and the eye relief greatly.